Stabilized organic compositions containing hindered phenolic thio succinates

ABSTRACT

ORGANIC MATERIALS, PARTICULARLY SYNTHETIC POLYMERS SUCH AS POLYPROPYLENE, ARE PROTECTED AGAINST OXIDATION IN AIR, THERMAL DEGRADATION OR DETERIORATION BY INCLUDING, IN SUCH SUBSTANCES, A STABILIZING AMOUNT OF AN ANTIOXIDANT. THE ANTIOXIDANT IS OBTAINED BY REACTING (A) AN A,B-UNSATURATED ESTER OF A HINDERED HYDROQUINONE AND (B) A THIO ACID.

United. States Patent @ffice Patented July 10, 1973 US. Cl. 260-45.85 S 10 Claims ABSTRACT OF THE DISCLOSURE Organic materials, particularly synthetic polymers such as polypropylene, are protected against oxidation in air, thermal degradation or deterioration by including, in such substances, a stabilizing amount of an antioxidant. The antioxidant is obtained by reacting (a) an a,,B-unsaturated ester of a hindered hydroquinone and (b) a thio acid.

This application in a division of application Ser. No. 803,115, filed Feb. 27, 1969, now US. 'Pat. 3,636,033, issued Jan. 1 8, 1972.

The present invention is concerned with novel compounds which are useful as antioxidants for organic materials and particularly, as antioxidants for synthetic polymers such as, for example, polypropylene, polyethylene, polyester, polystyrene, polyvinyl chloride, nylon and other polyamides, cellulosics, polyacetals, polyurethanes, petroleum and wood resins, mineral oils, animal and vegetable fats, waxes, rubbers such as styrene-butadiene rubber (SBR), acrylonitrile-butadiene-styrene rubber ([ABS), olefin-copolymers, ethylene-vinyl-acetate copolymers, polycarbonates, polyacrylom'trile, poly (4-methyl pentene-l) polymers, polyoxymethylenes, and the like. The present invention also relates to a novel procedure for preparing the aforesaid novel antioxidants and to stabilized compositions containing said novel antioxidants.

The prevention of oxidation of various organic materials is obviously of primary industrial concern and therefore, antioxidants are used in or added to a wide variety of commercial products such as synthetic polymers of the type indicated supra, oils, plastic materials, etc., which are normally subject to oxidative deterioration.

The novel antioxidants of the present invention are represented by the following formulae:

R R I" R R IUCOS--H R C S-(J-(JH I 0 OR L it A) 0 OR a Formula I Formula 11 wherein R is (lower) alkyl (lower) alkyl R R'*, -R are each hydrogen, lower alkyl, aryl,

aralkyl or -C H OO0R, where m is 1 to 6 -R is straight or branched alkyl, aryl, aralkyl or R ---R is -C,,-H wherein n is 1 to 12 or C H (ortho, meta or para phenylene) As used herein, alkyl covers straight, branched and cyclic alkyl groups having from 1 to 24 carbon atoms and preferably to 12 carbon atoms; lower alkyl covers groups containing from 1 to 6 carbon atoms. Illustrative examples of such groups are methyl, ethyl, isopropyl, n-butyl, t-butyl, n-hexyl, n-octyl, n-decyl, n-dodecyl, n-hexadecyl, n-eicosyl, n-tetracosyl and the various branched chain isomers thereof. Aryl and aralkyl include phenyl, naphthyl and alkyl substituted phenyl or naphthyl groups having up to 24 carbon atoms. Illustrative examples are benzyl, phenylethyl, 2,4-dibutylphenyl, 2,4,6-trihexylphenyl, 6-phenylnaphthyl, 2-naphthylethyl, 2-naphthylhexyl and the like. In addition, aryl and aralkyl can also be substituted by a halogen, alkoxy, hydroxyl, alkylthio or arylthio group. Illustrative examples of such groups are 4-chlorophenyl, 4-bromobenzyl, 2-(4-chloronaphthyl), 4-ethoxyphenyl, 2 (4 methoxynaphthyl), 4-hydroxy-3- methylphenyl, ethylthiophenyl, 4-butylthiophenyl, 3-hydroxy-4-ethylthiophenyl, 2-(4-ethy1thionaphthyl), and the like. A preferred aralkyl group is benzyl. Where R R and R is C,,,H COOR, m can be 0 to 6 but preferably 0 or 1.

Illustrative examples of alkylene groups having 1 to '12 carbon atoms are methylene, tetramethylene, hexamethylene, dodecamethylene, ethylene and the like.

The novel antioxidants of the present invention are addition products of (a) an oz,B-unsaturated ester of a hindered hydroquinone of the formula and (b) a thio acid of the formula R COSH or I-ISCO -N-COSH,

wherein R, R R R R and R are as described above. Instead of the free thio acids, their salts, such as the sodium or potassium salts can also be used.

The addition reaction involving the c p-unsaturated ester and a thio acid is accomplished by simply reacting the two reactants, preferably in an inert solvent, at elevated temperatures from 30 to 120 C. from 30 minutes to 48 hours. If the free thio acids are used in the addition reaction the conversion can be accelerated by the addition of catalytic amounts of a base such as sodium or potassium methoxide or ethoxide, piperidine or benzyltrimethylammonium hydroxide. It is also possible to catalyze the addition reaction by the use of a freeradical initiator such as an azo compound and particularly an azonitrile compound or an aliphatic peroxide of the type described in applicants copending application entitled Polymeric Antioxidants, Ser. No. 738,770, filed June 21, 1968. The free-radical initiators, however, can be used only if the nap-unsaturated esters of a hindered hydroquinone shows little or no tendency toward the free-radication polymerization.

The addition reaction of cap-unsaturated esters and thio acids as such is well known and described in Houben-Weyl, Methoden der Organischen Chemie, vol. IX, pages 750-752 (Georgy Thieme Verlag, Stuttgart, 1955) and in Reactions of the Acrylic Esters by E. H. Riddle, page 149 (Reinhold Publishing Corp., N.Y., 1954).

The novel antioxidants of this invention were prepared by using the following procedure:

Equimolar amounts of the rigs-unsaturated ester and the thio acid were dissolved in three times the amount of chloroform and sealed in a reaction vessel under nitrogen. The vessel is 'kept from 12 to 2.4 hours at 80 C. depending on the degree of conversion which was checked by thin layer chromatography. After completion of the reaction, the solvent is evaporated and the crude product is purified by recrystallization from hexane, heptane or benzene, and identified by infrared spectroscopy, nuclear magnetic resonance and elemental analysis as indicated in Table I. Yields are high, that is, higher than Illustrative il-unsaturated esters used in preparing the desired antioxidants of the present invention as indicated above, are represented by the following formula:

wherein R is (lower) alkyl (lower) alkyl and R R and R are as defined above.

Examples of such esters are:

R R B.

Esters of:

Acrylic acid H H H Methacrylic acid H -H -CH; Crotonic acid..- CH3 --H -H Cinnamic acid.. CoHn --H -H Fumaric acid--. -COOR -H H Maleic acid- -O0OR H Mesaconic acid. COOR CH; Citraeonic acid -COOR CH; Itaconic acid.. -H -H -CH2COOR Aconitic acid- --CO0R -H CH2COO R compounds used in preparing the antioxidant compounds of the present invention are as follows:

(a) 3,5-di-tert-buty1-4-hydroxyphenylacrylate CH =CH-COOR (b) Bis(3,5-di-tert-butyl-4-hydroxyphenyl)fumarate H 02011,, H (c) Bis(3,5-di-tert-butyl-4-hydroxyphenyl)itaconate CHpC-C O 0R Hr'COOR COORo wherein R is The aforesaid n e-unsaturated esters (identified above as compounds (a), (b) and (0)) are reacted with the following thio acids:

(1) Thioaeetic acid CHQCOSH e) Thiopropionic acid" CHgCHgOOSH (t) Thiobenzoic acid CGHBCOSH (g) Diphenylthioacetic acid (CaHmCHOOSH (h) Dithioterephthalic acid H S C 0- C O S B Table I below contains illustrative examples of the antioxidants of this invention with their properties and most of them with elemental analysis. These antioxidants have been prepared by the addition of the thio acids to the a,fl-unsaturated esters according to the general pro- Some of the preferred starting a,,3-unsaturated ester cedure described above.

TABLE I.-PROPERTIES AND ANALYSIS OF NOVEL ANTIOXIDANTS Elemental analysis Melting point, Calculated Found crystallized Starting Appearance from- C H S C H 8 materials Product White crystals- 1025512330., 64. 74 8. 01 9. 09 64. 77 7. 89 9. 02 (a)+(d) 3,5-dZI-tert-butyM-hydroxyphenyl 3-(acetylthlo)proplo- (A) e na 0 RoOCO CHzCHlSCOCH:

Dotoo-102 0., 73. 77 7. 19 6. 35 73. 89 7. 27 6. 29 (AH-(x) 3,5-dl-tert-butyl-khydroxyphenyl 3-(diphenylacetylthio)- (B) hexane. propionate R00 0 O CHQCHgSC O CH(C|H5):

White flakes- 65.5-66-5 0., A. (bH- (d) Bis(3,5-di-tert-butyl4-hydroxyphenyl) 2-(acetylthlo)- (C) heptane. succinate ROOCOCHBCO CH;

RnO O 0 H 1 D0. 6365 0., 68. 37 8. 20 5. 21 68. 83 8. 48 5. 21 (b)+(e) Bis(3,5-di-tert-butyl-t-hydroxyphenyl) 2-(propiony1thlo)- (D) hexane. succlnate R00 00 CHSC O CHaCH:

R00 0 O H;

White crystals" 56 0 (c)+'((e) Bls(3,5-di-tert-butyli-hydroxyphenyl) 2-(proplonylthlo- (E) hextane. methyDsnccinate R00 00 CHCHaSC O CHzCH:

R 0 0 0 HI White flakes. 63 0. (sin- 70. 66 7. 4. 83 71. 09 7. 79 4. 79 (b)+(0 Bls(3,5-di-tert-butyl4-hydroxyphenyl) 2-(benzoylthlo)- (F) 22153 hepsuccinate ROOCOCHSCOCGHB R00 C 0 CH1 Do- 66 0. (sin- 70. 97 7. 74 4. 74 70. 67 7. 87 4. 38 (c)+(f) Bls(3,5-dl-tert-but 1-4-h drh 2- ages) hexrncthylsuccinatgj y Oxyp enyl) (bemoylthio. (G)

" RoOCOCHCHfiCOCcH;

390 CO H;

TABLE I-Continued Elemental analysis Melting point, Calculated Found crystallized Starting Appearance from- O H S C H 8 materials Product White crystals 165166.5 0.,

Bis(3,5-di-tert-butyM-hydroxyphenyl)3,3-(terephthalo- (H) heptane/ ylthio dipropionate benzene.

(RQOCOCHICHQS oo Do 7274 0., 73. 37 7.50 4. 26 73.79 7.50 4.12 (b)+(g) Bis(3,5-di-tert-butyl-4 hydroxyphenyl) Z-(dipehnylaeetyl- (I) hexane. thro)succ1nate R00 C 0 CHSCO CH(C6H5)| R 0 0 O H:

hi owder... Slnters 110 (bH-(h) Tetraki (3,5-di-tert-butyl-4-hydroxypheny1) 22'- (J) W m p 0., hep- (terephthaloylthio)disuccinate tame/ben- (mooor ins oo R00 C O CH: 2

185l87 O. 69.67 7.74 5.03 69.76 7. 66 5.02 (0)+(h) Tetrakis(3,5-di-tert-butyl-4-hydroxyphen 1) 22- (K Do haptanel terephthaloylthiomethyl)disuccinate y benzene.

IV, pages 745-747 (Georg Thieme Verlag, Stuttgart, 5

1955). The synthesis of all a,}8-unsaturated esters containing hindered penolic groups is described in my copending application Ser. No. 738,770, filed June 21, 1968.

(R00 00 onoms co- 2 R 0 0 O CH;

One general method for preparing said unsaturated esters comprises reacting an alcohol dissolved in pyridine with an acid chloride. For example, 2,6-di-t-butylhydroquinone and acrylyl chloride yield 3,5-di-t-butyl-4-hydroxyphenyl acrylate; 2,6-di-t-butylhydroquinone and methacrylyl chloride yield 3,5-di-t-butyl 4 hydroxyphenyl methacrylate; 2,6 di-t-butylhydroquinone and fumaryl chloride yield 'bis(3,5-t-butyl 4 hydroxyphenyl) fumarate; 2,6 di t butylhydroquinone and itaconyl chloride yield bis(3,5 di-t-butyl 4 hydroxyphenyl) itaconate.

TABLE II Antlox. type Thio acids 0:, B-Unsaturated esters Novel antioxidants I CH CH GOSH R ocoons CH a( a): :CCHCOORO) trans 0 C0( MGR: (L) 2 R00 00 on, I OHAOHmCOSH CH2=C00OR0 mooocnomsoowmnom (M) CHgCOOB-u RQOCOCH:

1 cnawna oosn CH2=CHCO0R0 RoOCOCHaCHzSCO(CH3)uCH (N) @CH2OOSH {oHoooR) ,trans a.ooooHsoooH,-@ (0) R00 00 on. r l (P) -s- COSH onooom ,trans mooocrrsco- -s- 1 i (Q) cnao- OOSH enooom ,trens mocoonsco- -oon.

GOSH Ruococmomsco 0 O 011,:01100012. 0

Ema-2:: oosn 2 on -00 R I T I k 00 o R.0o0oHcH.so0-

11.000170 R00 00 CH: .L

II T {011.cosn) 2 CHCOORo) ,trans [mooocnsooom mo 00 on, .L II...:.'..-;::: [OH H (U) T ,0 ,oosH 2 CHS=C(CH3)OOOR0 Ro000oH(oH.)oH,so0cH.oH,-

No'rE.-R 0 H, 3,5-di-t-butyl-d-hydroxyphenyl.

The oxidation of most polymers is so slow at ambient temperatures, even in the absence of antioxidants, that testing of the eifects of antioxidants must necessarily be conducted at high temperatures in order to yield results within a convenient period of time. The tests conducted on the materials listed in the following Tables III and IV v were conducted either in a tubular oven with an airflow of 400 cubic feet per minute at an oven temperature of 150 C. or a rotary oven with 4 rpm. at an oven temperature of 150 C. The oven aging is expressed in hours.

In preparing the sample for testing, unstabilized polypropylene powder is thoroughly blended with the indicated antioxidant. The blended material is thereafter milled on a two-roller mill at a temperature of 182 C. for six minutes after which time the stabilized polypropylene is sheeted from the mill and allowed to cool. The milled polypropylene sheet which has been stabilized is then cut into small pieces and pressed for seven minutes on a hydraulic press at 218 C. and 174 p.s.i. pressure. The resultant sheet of 25 mil thickness is then tested for resistance to accelerated ageing in the above described tubular oven. In Table II and IV are reported the results of the oven ageing tests in which the antioxidants of this invention were added to polypropylene together with the indicated ultra-violet light absorber and the synergist.

TABLE TIL-EVALUATION OF NOVEL ANTIOXIDANTS IN POLYPROPYLENE (25 MIL), TUBULAR OVEN, 150 C.

Hours to fail 0.1% antloxidant plus 0.25% anti- 0.5% 2, oxidant plus plus 0.3% Product 0.5% UV-2 DSTDP 1 1 UV-2, an ultraviolet absorber, 2-(3',5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotralzole.

idDsIDP=distearylthlodiproplonate, commercial synergist for antiox an s.

Note.Unstablllzed-3 hours.

TABLE IV.-EVALUATION OF NOVEL ANTIOXIDANTS IN POLYPROPYLENE (25 MIL), ROTARY OVEN, 150 0.

Hours to fail 0.1% antioxidant plus 0.25% antl- 0.5% UV-2 oxidant plus plus 0.3% 0.5% UV-2 STD Note.-Unstabillzed-2 hours.

Results similar to those reported in Tables III and IV are obtained when the antioxidants of Table II are employed together with the indicated secondary antioxidants and ultraviolet absorbers.

T DLTDP=Dllaurylthiodiproplonate.

It should be noted that in all above examples of stabilizing compositions the use of a secondary antioxidant and an ultraviolet absorber is optional. However, for best results, said additives should be employed in conjunction with the antioxidants of this invention, especially the secondary antioxidant. These additional additives may be used in the amount of from about 0.05 to about 5% each, and preferably from about 0.1 to about 2% by weight of the substrate.

Besides activity in the oven ageing test, the novel antioxidants of the present invention are characterized by excellent color values (no discoloration during the oven ageing test) and good gas fading properties.

The present antioxidants are useful in protecting synthetic polymers such as polypropylene against oxidation in air, thermal degradation or deterioration by including in such substances, a stabilizing amount of the antioxidant which will vary between about 0.01 and 5% and preferably, from about 0.05 to about 1.0% by weight. The antioxidant can be incorporated into the synthetic polymers using conventional procedures. For example, the antioxidants of the present invention are incorporated into the material to be stabilized by any suitable means such as by milling the antioxidant on hot or cold mill rolls, by mixing it in by the use of a Banbury mixer or other well-known devices of this nature or the antioxidant may be mixed with a polyolefin material in the form of molding powder and incorporated during extrusion or prior to extrusion or during injection molding. The antioxidant may even be incorporated into a solution of the polyolefin material and the solution may then be employed for the formation of films, for wet or dry spinning of fibers, monofilament and the like.

The examples set out above are to be considered as illustrative of the present invention and are not to be considered as restrictive. It is therefore to be understood that the invention is not limited to the specific embodiments set out above except as defined in the appended claims.

What is claimed is:

1. A composition of matter stabilized against deterioration comprising an organic material normally subject to deterioration and from 0.01% to 5.0% by Weight of said organic material of an antioxidant compound having the formula (lower) allryl (lower) alkyl 2 wherein -R -R -R are each hydrogen, lower alkyl, aryl, aralkyl or --C H COOR, where m is 1 or 2, such that only one of said R R and R is 2. A composition of matter according to claim 1 wherein said antioxidant compound is selected from 3,5-di-t-butyl-4-hydroxyphenyl 3-(acetylthio) propionate,

3,5-di-t butyl-4-hydroxyphenyl 3-(di-phenylacetylthio) propionate,

bis(3,5-di-t-butyl-4-hydroxyphenyl) Z-(acetylthio) succinate,

bis(3,5-di-t-butyl-4-hydroxyphenyl) 2-(propionylthio) succinate,

bis(3,5-di-t-butyl-4-hydroxyphenyl) Z-(propionylthiomethyl)succinate,

bis(3,5-di-t-butyl-4-hydroxyphenyl) 2-(benzoylthio) succinate,

9 bis(3,5-di-t-butyl-4-hydroxyphenyl) 2- (benzoylthiomethyl) succinate, bis(3,5-di-t-butyl-4-hydroxyphenyl) 3,3'-(terephthaloylthio dipropionate, bis(3,5-di-t-butyl-4-hydroxyphenyl) Z-(diphenylacetylthio) succinate, tetrakis(3,5-di-t-butyl-4-hydroxyphenyl) 2,2-(terephthaloylthio disuccinate, tetrakis(3,5-di-t-butyl-4-hydroxyphenyl) 2,2-

(terephthaloylthiomethyl disuccinate.

3. A composition of matter according to claim 2 wherein said organic material is polypropylene.

4. A composition of matter stabilized against deterioration comprising an organic material normally subject to deterioration, from 0.01 to of an antioxidant having the formula 1%." DOOOH (lower) alkyl 2 wherein -R --R R are each hydrogen, lower alkyl, aryl, aralkyl or --C H COOR, where m is 1 or 2, such that only one of said R R and R is and from 0.01 to 5% of a secondary antioxidant selected from dilaurylthiodipropionate and distearylthiodipropionate.

5. A composition of claim 4 wherein said organic material is poly propylene.

6. A composition of claim 5 wherein said antioxidant 1's bis( 3,5 di-tert-butyl-4-hydroxypheny1)-2-benzoylthiomethyl) succinate.

7. A composition of claim 5 wherein said antioxidant References Cited UNITED STATES PATENTS 3,285,855 11/1966 Dexter et al 260-4585 3,294,836 12/1966 Peterson et a1. 260-4585 3,345,327 10/1967 Dexter 26045.85 3,433,762 3/ 1969 Kezerian et al 260-4585 3,536,661 10/1970 Hagenrneyer et a1. 26045.85 3,598,854 8/1971 Steinberg 26045.85

MAURICE J. WELSH, Primary Examiner V. P. HOKE, Assistant Examiner US. Cl. X.R. 

